This invention relates generally to a cooling assembly, and more particularly to, a cooling assembly for an X-ray tube for transferring heat away from components of the X-ray tube. The X-ray tube with cooling assembly can be used in applications related to medical diagnostics, industrial imaging and crystallography.
In an X-ray tube, a beam of electrons is directed through a vacuum, across very high voltage, from a cathode to a focal spot position on an anode. X-rays are produced as electrons strike the anode, comprising a refractory metal track, such as tungsten, molybdenum or rhodium. However, the conversion efficiency of X-ray tubes is quite low, typically less than 1% of the total power input. The remainder, in excess of 99% of the input electron beam power, is converted into thermal energy or heat.
Accordingly, heat removal or other effective procedures for managing heat tends to be a major concern in the design and operation of an X-ray tube. Very high temperatures in the X-ray tube can result in increased cooling times, target melt, and anode bearing lubricant delamination and/or evaporation. These cooling problems result in X-ray tubes having lower power capability, larger anodes and increased load on the anode bearings, larger heat exchangers, and higher flow rates of coolant. To attain a higher power capability of an X-ray tube, a larger anode is typically required, resulting in a larger X-ray tube.
Some of the solutions in the prior art for removing heat from or cooling X-ray tubes include rotating the target and increasing heat storage capacity by attaching a piece of graphite to the target. Attempts have been made to cool the target convectively by passing a coolant through the anode. One disadvantage of this method is the requirement of a non-contact or contact seal to seal a vacuum region between the anode and frame of the X-ray tube. Another method in the prior art attempts to cool the target by attaching the target to the X-ray tube frame assembly and rotating the frame assembly. This would require a high capacity motor with high power requirements to rotate the frame assembly and also beam deflection technology to deflect the electron beam on the target to obtain a good focal spot.
Thus, it is desirable to provide a cooling assembly for an X-ray tube, which provides excellent thermal efficiency, and is easy to manufacture, less expensive and less complicated from prior art cooling systems. There also exists a need for adapting an efficient cooling assembly to existing X-ray tubes without having to completely redesign the existing X-ray tubes.